1. The Field of the Invention
The invention relates to a five-layered, biaxially oriented, shrinkable, sealable tubular film with improved oxygen barrier and to its use for the packaging and wrapping of paste-like foodstuffs, meat, and meat with bones.
2. Description of the Background
A five-layered, polyamide-based tubular film for packaging and wrapping pasty foodstuffs, especially a sausage skin, is already known from DE 43 39 337 C2. This tubular film is comprised of an inner layer and an outer layer made of the same polyamide material, a middle polyolefin layer and two adhesion-promoting layers made of the same material and situated between the inner layer and middle layer and between the middle layer and outer layer. The inner and outer layers consist of at least one aliphatic polyamide and/or at least one aliphatic copolyamide and at least one partially aromatic polyamide and/or at least one partially aromatic copolyamide, the amount of partially aromatic polyamide and/or copolyamide being from 5 to 60 wt.-%, relative to the total weight of the polymer mixture of partially aromatic and aliphatic polyamides and copolyamides. Such a tubular film, produced by coextrusion, is provided with controlled shrinkability by biaxial stretching and heat-setting. With respect to its technological properties important to wrapping and packaging of meat, especially meat with bones, such a tubular film requires some improvements. In the event of meat with bones there is a risk of protruding bones piercing the packaging film following shrinking of the packaging film on the packaged item, because the puncture resistance is insufficient. Furthermore, such tubular films for packaging and wrapping meat or meat with bones and pasty foodstuffs should also allow sealing by simple heat-sealing. With bags produced using such tubular films, the strength of the seal seam is a crucial issue. For example, when a piece of ham or meat drops out of a spout and into a bag made of a plastic film and sealed at its bottom by a heat-seal seam, considerable loads—depending on the weight—arise due to the product to be packaged dropping into the bag, possibly giving rise to tearing of the heat-seal seam and complete opening of the bag at the bottom thereof. Also, the heat-seal seam is exposed to extreme load during subsequent vacuum treatment and shrinking of the bags. Likewise, shipment and storage of the filled bags involve high demands on the puncture resistance of the film and on the seal seam strength.